A novel anti-browning agent S-furfuryl thioacetate for fresh-cut potato screened from food-derived sulfur compounds

Abstract

This research aimed to screen out safe and effective inhibitors of enzymatic browning from food-derived sulfur-containing compounds. Among eighteen candidate compounds, three were found to reduce the browning of fresh potato mashes. One of these compounds, S-furfuryl thioacetate (S-Ft) at only 0.04 and 0.07 mM inhibited the browning of fresh potato sticks, for over 10 d at 4 °C with an efficacy close to sodium bisulfite at 2.40 mM. S-Ft also reduced the browning of eggplant and asparagus lettuce slices. S-Ft retarded the browning occurrence of potato mashes and tyrosine solutions, but it did not cause the brown pigments colorless. Both the decrease in tyrosine contents and the increase in quinone contents were slowed by S-Ft in potato mashes. Compared with control, S-Ft at 0.04 and 0.07 mM reduced polyphenol oxidase (PPO) activity by 91.22 % and 91.77 %, and addition of copper acetate recovered the PPO activities to 55.62 % and 59.45 % of control, respectively. Kinetics results showed S-Ft inhibited PPO activity in a reversible mixed-type manner. The data of circular dichroism analysis and fluorescence emission spectra indicated S-Ft treatment caused the decrease in α-helix content, the increase in β-sheet content and the change in secondary structure of PPO. Molecular docking results illustrated S-Ft could act with Cu2+ and amino acid residues of PPO. By comparison with other anti-browning inhibitors, S-Ft has the characteristics of low dosage and long shelf-life extension. These results demonstrated that S-Ft could be a novel and promising enzymatic browning inhibitor by chelating Cu2+ and changing the conformation of enzyme to reduce PPO activity.